Calculation of the optimal architecture of a double-layer ITO film intended for use in reflective contacts in blue and near-UV LEDs

Reflection from multilayer coatings serving as contacts in AlInGaN light-emitting diodes (LEDs) is calculated in terms of a model based on the transfer-matrix method. ITO/SiO$_2$/Ag composites with an ITO film constituted by two layers with different refractive indices are considered. The thicknesses of the ITO layers are varied within a prescribed range. The angular dependences of the reflectance for light of both polarizations are calculated, and the integrated reflectivity of a contact is obtained on this basis. The dependence of the integrated reflectivity of the contact and that of the reflectance of light incident perpendicularly to the plane of the contact on the thickness of the ITO layers are analyzed. As a result, the optimized architecture of a reflective contact to the $p$-GaN region of AlInGaN LED chips is suggested.